The present invention relates to a handheld machine tool, in particular an electric screwdriver.
U.S. Pat. No. 5,398,946 A describes an electric screwdriver into whose tool mount can be inserted a screwdriver bit without operation of the tool mount. The screwdriver bit can be removed by shifting an actuating sleeve together with the tool in a common direction of removal.
The handheld machine tool according to the invention has an electric motor and an output spindle, which can be driven by the electric motor to rotate about a working axis. The output spindle has a cylindrical or prismatic intake space that is open on the output side and is oriented along a working axis to receive a tool in the direction opposite the removal direction and also has two elongated holes inserted into the intake space in the radial direction. A blocking element, which protrudes into the intake space, lies in the elongated hole and is movable between one end of the elongated hole on the output side and one end of the elongated hole on the drive side. The blocking element is forced into engagement in the intake space, in contact with a radial stop in the radial direction. In a locking position, the stop overlaps with the ends of the elongated holes on the output side and is displaceable in the removal direction opposite a spring force of a spring to release a radial movement of the blocking element out of engagement with the intake space. A spring has a support ring and two bows protruding away from the support ring in the withdrawal direction, curved in the form of a segment of a circle around the intake space, each of the bows having a pin that engages radially in the elongated hole in the withdrawal direction upstream from the blocking element.
The spring-action bows press the blocking elements into a locking position so that they are hindered from yielding radially out of the intake space. On insertion of a tool, the user can shift the blocking elements together with the bows toward the end of the elongated holes on the drive side. The blocking elements can yield radially here.
The spring with the bows, which are preferably designed with radial symmetry, is very compact. Furthermore, the symmetrical design, in particular mirror-symmetrical, design, prevents transverse forces, which can result in tilting of components with respect to the working axis and can lead to a potential skewing.
One embodiment is characterized in that the support ring is slotted and the two bows are each attached on one side of the slot. The bows may be inclined by a clearance angle with respect to the support ring, in particular in a relaxed state of the spring. The bows preferably only partially span the working axis, for example, by less than 180°, e.g., for approximately 90°.
One embodiment provides that the support ring, the bows and the pins are formed from a cohesive piece of wire.
One embodiment provides that a ramp is connected to the radial stop opposite the withdrawal direction. The ramp has a surface opposite the withdrawal direction and at a distance from the working axis. The blocking elements deflected when the tool is inserted experience a force in the withdrawal direction due to the spring, this force being deflected by the curtain formed by the ramp into a force acting partially toward the working axis. The blocking elements are thereby guided securely in engagement with the intake space and the tool situated therein.